title: A prospective dual-energy X-ray absorptiometry study of bone remodeling after implantation of the Nanos short-stemmed prosthesis.
abstract: The aim of this study was to analyze the bone remodeling around the Nanos stem (Smith & Nephew, Marl, Germany) after primary total hip arthroplasty for coxarthrosis. In 25 patients (15 male, 10 female, mean age 59.9 years) with the diagnosis of coxarthrosis, a DEXA scan was performed immediately after surgery, 97 days (SD 6.1 days) and 368 days (SD 6.2 days) after implantation of a Nanos prosthesis. Plain radiographs were analyzed digitally for radiolucent lines, varus-valgus femoral stem alignment, measurement of stem migration and changes in varus-valgus femoral stem alignment. The position of the center of rotation (COR) and the offset were assessed pre- and postoperatively. Harris Hip Score was used to evaluate the clinical outcome. The DEXA scan showed a significant and relevant increase in BMD (Bone Mineral Density) in Gruen-Zone 6 (12%) and a decrease in Zone 1 (15%), 2 (5%) and 7 (12%), which was interpreted as reflecting a distal load transfer in the metaphysis of the femur. There was no clinically relevant migration or tilting of the Nanos stem. Radiolucent lines were noted in 12 cases, mainly at the polished tip area of the prosthesis; this was not regarded as a sign of impaired osseointegration. There was no significant difference between the position of the COR and the pre- and postoperative offset. The absence of stem migration, angulation, or relevant radiolucent lines is seen as evidence for an unimpaired osseointegration of the Nanos stem approximately 12 months after implantation. It is concluded that the Nanos prosthesis can reduce loss of BMD of the proximal femur composed with conventional stems or other short-stemmed implants.
authors.affiliation: Department of Orthopaedic Surgery and Traumatology, Martin-Luther-University of Halle-Wittenberg, Faculty of Medicine, Halle/Saale, Germany. alexander.zeh@uk-halle.de
authors.forename: Alexander
authors.initials: A
authors.lastname: Zeh
authors.forename: Franziska
authors.initials: F
authors.lastname: Pankow
authors.forename: Marc
authors.initials: M
authors.lastname: Röllinhoff
authors.forename: Stefan
authors.initials: S
authors.lastname: Delank
authors.forename: David
authors.initials: D
authors.lastname: Wohlrab
mesh_terms: D015502:Absorptiometry, Photon; D000368:Aged; D019644:Arthroplasty, Replacement, Hip; D015519:Bone Density; D016723:Bone Remodeling; D005260:Female; D005269:Femur / Q000503:physiopathology*; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D011184:Postoperative Period; D011446:Prospective Studies